Microreactors
present innovative solutions for problems pertaining
to conventional reactors and therefore have seen successful application
in several industrial processes. Yet, its application in heterogeneously
catalyzed gas–liquid reactions has been challenging, mainly
due to the lack of an easy and flexible methodology for catalyst incorporation
inside these reactors. Herein, we report a facile technique for obtaining
small (<2 nm) and well-distributed catalytic nanoparticles on the
walls of silica-coated capillaries, that act as micro(channel) reactors.
These particles are formed in situ on the reactor walls using polyelectrolyte
multilayers (PEMs), built by layer-by-layer self-assembly. Manipulating
the PEMs’ synthesis condition gives easy control over metal
loading, without compromising on particle size. Both monometallic
(Au and Pd) and bimetallic (AuPd) nanoparticles were successfully
obtained using this technique. Finally, these catalytic microreactors
were found to exhibit exceptional activity for the direct synthesis
of hydrogen peroxide from H2 and O2.
Direct synthesis represents a green alternative, an environmentally benign process for the production of hydrogen peroxide. This is a three‐phase reaction, a solid catalyst with gas reactants and a liquid phase, which collects hydrogen peroxide formed from the catalyst surface. The choice of solvent and/or addition of promoters has a significant effect on the reaction rates observed, as well as selectivity towards peroxide. In addition to non‐toxic water, short chain alcohols are very attractive, due to good solubility of reacting gases. Here we report an extensive study on the influence of different groups of solvents on the direct synthesis reaction when either applied alone or as co‐solvent under non‐explosive and conventionally explosive reaction conditions.
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